Error message when Java Script is turned off

Everything works fine with Javascript enabled in the browser; when it is turned off, the (new) share page opens as it should, but it also displays a nasty error message:

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'forward_form' was given in /var/www/drupal-5.2/includes/form.inc on line 217.

This happens with the latest Firefox and Internet Explorer with my own theme (Pushbutton based) as well as with Garland.